Sensitivity of circuit peak thermal performance to convective and geometric variation

A prototype electronic device consisting of two boards with multiple power dissipating components in a vented enclosure is studied for its thermal performance under forced and natural air cooling conditions. The internal geometry and physical orientation are also varied. Results in terms of effective board thermal resistances and local heat-transfer coefficients are reported. Forced convective resistances were a factor of five smaller than natural convection values. Physical orientation is seen to be the second most important sensitivity after convection mode due to the potential for local buoyancy effects. Overall thermal performance can be affected by as much as 25% due to non-convection-mode-related variations. Design implications as well as the applicability of the data to analysis method validation are discussed